Telegraph system



April 18, 1939. F, E, D'HUMY ET AL 2,154,441

TgLEGRAPH SYSTEM Original Filed Jun 18, 1935 2 Sheets-Sheet l ORNEY April 18, 1939. F. E. DHUMY ET AL 2,154,441

TELEGRAPH S YSTEM Original Filed June 18, 1935 2 Sheets-Sheet 2 Tox ' law i I g u Y o u [L 4 2 g 5 k I INVENTOR a F.E.d'HUMY L g 1 s 5 BY I LWFRANNJN ATT RNEY NITED] ST T s PATENT OFFICE;

Company, New

,New York 1 Application 310kbps.- This invention relates to telegraph systems and more particularly. to the transmission of tele- Y with signals over standard telephone circuits.

' In 'acopending application of F. E. dHumy and j. L'. w. Franklin, Serial No. 17,842,flied April 23,

'1935, there is disclosed a system for carrying on telegraph correspondence over a standard telephone circuit by tone or audible signals. Briefly the invention of said application comprises producing oscillation of a frequency within the audible range, keying such oscollations in accordance with'a telegraph code andapplying aid keyed oscillations to, a tone producing device acoustically shielded and coupled to 'a standard, telephone "transmitter. to produce electrical variations or trains of oscillations in. the telephone circuit.' At the receiving end of the telephone circult, the received signals are rectified and filtered 'so as to enable a standard telegraph receiver to respond thereto.

, 'The'presentinvention is an improvement on.

the invention of the aforesaid application, one of 1 the objectsthereof'being to permit simultaneous transmission of voice signals and telegraph sig nals over a standard telephone circuit without Another object. is to provide an improved plural channel communication system Other objects and advantages of the'invention will hereinafter appear.

The invention will be more fully understood by reference to the accompanying drawings in which.

Fig. 1 is a circuit diagram of a" telegraphictelephone' transmitting and receiving system embodying certain features of the present invention:

Fig. 2 is adiagram of the signals as they appear invarious parts of-the system: and

' l 'ig. 8 is a-circuit diagram of a'modifled form of the system. employing a plurality offcha'nnels v of telegraph communication.

Referringflrst tong; 1, there is shown a systern for the' simultaneous transmission of,tele-' graph aindyvoice'signals. thereby permitting telegraph communication tobe maintainedover a standard telephone system without interferingwith' ordinary telephoneconversation thereover.

Two source's ofelectrical oscillations, Pi and F2. are provided; Th y" may beva'cuum tube .oscillators; small aiternatojrs' of the' Alexanderscn type, a microphone 1 bowler.) a" tuning fork .con-

June 18, 1935, Renewed March 9, 1

ren W. Franklin, Hasbrouck' Heights, N. 1., asdg'nors to The Western York -MI acorporation-of Union Serial No. 27,! 988 (Cl. 178-!) I trolled means or other well known form of oscillatorof the proper frequency. Source Pi is labeled 2500 cycles per second and source F2 is marked 800 cycles per second. These values are arbitrary, however, and other frequencies wi hin reasonably wide limits may be employed. e source Fl isleft unkeyed while thesource F2 is keyed by a standard telegraph transmitter which may be either a keyboard transmitter or a storage transmitter such as a tape controlled transmitting 1o distributor. A start-stop transmitter of the latter type isdisclosed in Patent No. 1,805,324 of Bothermel, granted May 12, 1931. In transmitting distributors of this type, the rest contact R of the transmitting distributor ID ,is closed when the transmitter is idle, so as to applya marking condition to the outgoing line and upon transmission of acharacter the rest contact is opened to transmit a spacing condition to the line. This is followed by successive closing of the code contacts i to I to complete circuits through the selectively closed contacts of the tape transmitter T. The rest contact R again closes following transmission of the fifth code impulse.

The oscillations from the source Fl are conti'nuously applied through the transformer iii to the grid of the vacuum tube VI. The oscillations from the source F2 are applied in accordance with a telegraph code to the cathode return circuit of tube VI. through the transformer Ii. The 80 frequency Fl .is thus modulated by the keyed oscillations from source F2. This modulation, of course. may be obtained by otherv well known methods such as those in common use in radio receivers of, the superheterodyne type. The outso put. of tube Vi is applied to a band pass filter BPFI adapted to pass frequencies between 2150 and 2850 cycles and to highly attenuate signals ofvother frequencies.

' In Fig. 2, curve (it) illustrates the steady car- 40 rier'frequency Pi as it is applied to the mixer tube Vi. Curve (b) shows the frequency source 1''] as keyed by the tape transmitter T. Curve (cl indicates the form of the signals after they have passed through the band pass filter BPI 'I. 46 Curve -(d) shows afstandard square toppedprinter signal for purpose of comparison with thecurves'dn and (c). I

The band pass filter BPFI may be of anyof the well known types now in common use. This 50 filter need not necessarily be of the sharp cut off 7 type since its chief function is to eliminate the fundamental frequency and low harmonics of the low frequency source F2. The frequencies which will'be'impressed upon this filter are FLVFI, s s

' quencies. Consequently if a frequency band'oi" from 2150 cycles to 2850 cycles is allowed to pass through the filter BPEI, this range of frequency may be employed for telegraph communication over a standard telephone circuit and the frequencies below about 2000 cycles down to about 2.00 cycles may be used for regular telephone conversation.

A separate telephone transmitter T1 'in circuit with a battery 13 is provided for telephone conversation over the telephone system. The voice frequencies picked up by the transmitter T1 are passed through a low pass filter LPFI, designed to highly attenuate all frequencies above about 2000 cycles. The. output from the filters BPFI and LPFI are passed through a coupling transformer l2 and from the secondary thereof applied either directly or through an amplifier (not shown) to a sound producing device 8'.

The sound producing device S is enclosed in a .sound insulating container I3, the open end of which may be placed in contact with the mouthpiece ll of a standard telephone transmitter 'I'l'i so that the composite telegraph tone signals and voice signals will be impressed on the diaphragm of the telephone transmitter and hence reproduced in the telephone receiver TR at the distant end of the telephone circuit.

The telephone and telegraph receiving apparatus comprises a demodulating system. The tone signals p oduced by the telephone receiver are picked up by a microphone M preferably enclosed in a sound insulating container I! having its open end disposed in contact with the telephone receiver TR. The signals produced in the microphone are amplified by amplifier tube V2 of conventional design and are applied through the output transformer II to a band pass filter BPFZ and a low pass filter m2, in tandem. The low pass filter LPF2 is designed to pass frequencies below 2000 cycles and to highly attenuate higher frequencies. A telephone receiver 'I'Rl is connected in the output circuit of the low pass filter and serves to reproduce the voice frequencies introduced into the telephone transmitter IT at the sending station. An amplifier A may be inserted between the low pass filter LPF2 and the telephone receiver TRI, if desired.

The band pass filter BPF2 is designed to pass the frequency band between 2150 and 2850 cycles,

the telegraph signals carried by this range of frequency being transmitted through a transformer I! to ademodulator system having automatic gain control means associated therewith. The secondary winding l8 of the transformer I?! is connected in the grid circuit of a three element vacuum tube V3 and the winding i9 is connected in the plate circuit of the two electrode vacuum tube V4. Since the.2500 cycle carrier frequency is being transmittted from the source Fl whether the 800 cycle frequency isimposed thereon or not, the voltage across the diode tube V4 may be used to generate the negative voltage applied to the grid of the tube V2, to reduce the gain of the tube V3 when strongsignals are being received.

It will be noted that the portion of the signal energy which is applied to'the rectifier tube V4 is received and produces a pulsating direct current voltage across the resistance RI. This voltage is smoothed or filtered by the combined action of resistance RI and condenser Cl and resistance R2 and condenser 02 and produces an added negative voltage, in addition to that produced by the plate current drop through the resistance R2.

This added negative voltage is applied to the grid of tube V2, and thus acts to reduce the amplification of amplifier tube V2. This added voltage is' proportional, or nearly so, to the received 2500 cycle component so that its action is to level out V2. It might equally well be applied to tube V:

by any of the means common to frequency converters, such as used in superhetrodyne radio receiving circuits. The mixing of the local 2500 cycle frequency with the frequencies passed by the filter BPF2 will result in a strong 300 cycle frequency in the output circuit of tube V3. The output circuit of tube V1 is coupled through the transformer 22 to a low pass filter LPFS designed to suppress the frequencies substantially above 300 cycles. A band pass filter designed to pass 300 cycle oscillations might equally, well be used. The output of the filter LPFS is applied in pushpull to the grids of tubes V5 andVt. The function of the tubes VB and V6 is to i'irectify the full wave trains of 300. cycle telegraph signals, and

the winding of the printer relay 23. The filament I return is made to the junction of resistance RI and R5. The grid return from the center tap of the output winding 24 of filter LPF3 is made to the negative end of the bleeder circuit. Therefore, the negative bias on tubes V5 and V6 is the voltage drop across resistance R5 and the plate voltage is the voltage drop across resistance R4. A filter condenser C3 tends to even the fiow of current through the winding of relay 2!. The current in the relay winding is substantially asshown in curve (d) of Fig. 2. The tongue of relay 23 is connected tov the selecting magnet of the printer P.

In the use of the system a call between telephone subscribers is made in the usual way using the transmitter 'I'Tl after whichthe calling subscriber couples his sound producing device S to ceiving earpiece respectively, of the same telephone instrument.

In long telephone lines it is sometimes the prac tice to use vodas relays or other voice operated devices'to restrict conversation to one direction tion can ot be conducted but isnecessary to operate one way at. a time orto employ 'a separate telephone tem for telegraph communication in each direction. Telephone conversation may, of course, at the same time be carried on over both of such telephone systems in the same direction as the printer signals.

It will be noted that the 300 cycle carrier fre-- quency is first modulated in accordance with the telegraph code signals and the 2500 cycle carrier, in turn modulated by the modulated, 300 cycle frequency. In Fig. 3 this-carrier-on-carrier system is shown in connection with the application of a number oftelegraph channels to a single standard telephone-system. 'In the modification of Fig. 3 the telephone channel is eliminated and in its place several additional carrier-on-carrier.

channels similar to the telegraph channel of Fig.

. l are operated.

In Fig. 3, three carrier-on-carrier channelsare shown although many more may be provided within the range of efficient telephone line transmission. Each channel has its "own main carrier frequency generator Fa, Fb, Fc, etc., and also its own modulator frequency source MFa, MFb, MFc, etc. Each modulator frequency is keyed by a telegraph transmitting distributor TDXa,

TDXb, etc. and appliedtoa modulating tube Va, Vb, Vc, etc., to which the frequency sources Fa, Fb, Fc, etc., are coupled, respectively. The.

'transmitter 'I'Il' of the telephone circuit.

The oscillators Fa, Fb and Fe may operate respectively, at frequencies of 2800 cycles, 2450 cycles and 2100 cycles and the filters BPFc, BPFb and BPFc may pass frequencies between the ranges 2950 to 2650, 2600 to 2300', and 2250 to 1950 respectively. The modulator frequency sources MFa, MFb and We may be of the order of 150 cycles per second. It is to be understood,

however, that these frequencies are arbitrary and may be varied.

The signals received over the telephone line 'L are picked up by the microphone M, amplified by the tube V2 and applied through transformer 2,6 to the band pass'filters BPFa, BPF'b, BPF'c,

the transmitting sta etc. These filters pass respectively the same frequencies as filters -BP BPFb, BPFc, etc., at

. The apparatus associated with the output of each of the filters BPFa, BPF'b, etc., is the same andfitherefore only that associated with filter BPF'a will be I described.

The signals passed by the filter BPF'a are applied through transformer'll to a three element tube V'3 and a two element rectifier tube V4. The function of tube V'l is similar tothat oi.

,tube V lof Fig. 1 except that-it is usedto' control the amplification of the frequency converter tube V3 instead of thatof the amplifier tube V2.

For this purposethe grid of tube V3 is connected through resistances R2 and Rl to the cathode I of the rectifier tube to thereby apply an added negative voltage to the grid of tube V'3 in proportionto the magnitude of the 2500 cycle signals received over the channel. A local source of oscillations Fa is alsoapplied to tube V3 and the output of the tube "is applied through transformer 28 to a low pass filter LPF'3. In the output circuit of the filter LI-F'S are rectifier tubes V5 and V'G'in push-pull arrangement, as shown in Fig. 1. The output of these tubes operates a relay 23 to control the printer P.

As is well known, the ordinary telephone does not'respond equally well to all frequencies over the audio range. By having an individual-automatic gain control tube V'l associated with each channel, this variation may be compensated for by the individual channel receiving means. This alloys a wider frequency spectrum to be utilized with correspondingly more channels. While a modulating frequency of 150 cycles per second is shown in Fig. 3, the exact frequency used as the modulating frequency as well as the channel spacing used will depend to a large extent on the number of channels desired and the economies involved, that is, whether the additional expense involved in the use of extremely efficient filters is justified by the extra channels obtained by their use.

Since the filters BPFa, BPFb, BPFc, etc., are exactly the same in characteristics as filters BPF'a, BPFb, BPFc, etc., it is obvious that when one way transmission at a time is used, the same filters may, by appropriate switching means, be used both for receiving and sending.

It will be noted, that in both modifications shown herein there have been no changes in the telephone circuit. The telephone may, therefore, be used for either telephone or telegraph communication or for. both. It is obvious that the invention'is not limitedto the particular form or values indicated but numerous changes may be made therein, within the scope of the invention.

What is claimed is:

1. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with a telegraph code, producing electrical oscillations of a higher frequency, modulating said latter oscillations in accordance with said keyed oscillations, utilizing said modulated oscillations to produce tone signals and impressing said tone signals on the transmitter of the telephone system.

2. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined fre- -quency, keying said oscillations in accordance I with a telegraphcode, producing electrical cs,-

electrical oscillations of a predetermined frequency, keying said oscillations in accordance witha telegraph code, producing electrical 0s cillations of a higher frequency, modulating said latter oscillations in accordance with said keyed oscillations, filtering said modulated oscillations to attenuate frequencies substantially above and below the frequency of said second mentioned oscillations, utilizing said filtered oscillations to produce tone signals and impressing said tone signals on thetransmitter' of the telephone system.

4. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with a telegraph code, producing electrical oscillations of a frequency above about 2000 cycles per second, modulating said latter oscllations in accordance with said keyed oscillations, filtering said modulated oscillations to attenuate frequencies below about 2000 cycles per second, utilizing said filtered oscillations to produce tone signals and impressing said tone signals on the transmitter of the telephone system.

5. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with a telegraph code, producing electrical oscillations of a frequency near the upper, range of efficient telephone transmission, modulating said latter oscillations in accordance with said keyed oscillations, utilizing said modulated oscillations to produce tone signals and impressing said tone signals on the telephone system.

, over a telephone system comprising producing electrical oscillations of a predetermined frequency,. key ing said oscillations in accordance with a telegraph code; producing electrical oscillations of a frequency near the upper range of efficient telephone transmission, modulating said cillations of a frequency near the upper range of efilcient telephone transmission, modulating said latter oscillations in accordance: with said keyed oscillations, filtering said modulated ostelephone communication over said telephone sys- I tem.

'8. The method of communication over a telephone system which comprises producing. telegraphically modulated oscillations of a frequency I band near the upper range of eflicient telephone pressing said tone signals and voice frequency signals on the transmitter of a telephone system.

9. The method of communication over a telephone system which comprises producing telegraphically modulated oscillations of a frequency band near the upper range of efficient telephone transmission and voice frequency signals having the frequencies within said band suppressed, utilizing said telegraphically modulated oscillations and said voice frequency signals to produce audible signals and impressing said audible signals on the transmitter of a telephone system.

10. The method of telegraph communication over a telephone system comprises producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with a telegraph code, producing electrical oscillation of a higher frequency, modulating said latter oscillations in accordance with said keyed oscillations, utilizing said modulated oscillations to produce tone signals, transmitting said tone signals over a telephone system, converting the received tone signals into electrical oscillations, translating said oscillations into telegraph code impulses and operating a telegraph receiver in accordance with said impulses.

11. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with a telegraph code, producing electrical oscillations of a higher frequency, modulating said latter oscillations in accordance with said keyed oscillations, filtering the higher frequency components of said oscillations, rectifying the lower frequency components thereof to produce telegraph code impulsesand operating a telegraph receiver in accordance with saidimpulses.

12. The method of telegraph communication over a telephone system comprising producing electrical oscillations of a predetermined frequency, keying said oscillations in accordance with .a telegraph code, producing electrical oscillations of a higher frequency, modulating said latter oscillations in accordance'with said keyed oscillations, utilizing said modulated oscillations to produce tone signals, transmitting said tone signals over a telephone system, converting the received tone signals into electrical oscillations, regulating the amplitude of said received oscillations in accordance with a characteristic of the telephone circuit and controlling the operation of a telegraph receiver in accordance with said received oscillations.

13. The method of telegraph communication which comprises producing a plurality of oscillations of difierent predetermined frequencies, independently modulating the oscillations of each frequency in accordance with a telegraph code,

concurrentlyimpressing said modulated oscillations on a tone producing device, transmittin ,the' tone signals so produced over a telephone circuit, converting the received tone signals into electrical oscillations, filtering out the oscilla tions of each.of said original frequencies; regu lating the amplitude ofthe oscillations of each of said frequencies independently in accordance with the transmission characteristics of the telephone circuit at each of said frequencies, and utilizing the oscillations of each frequency to control the operation of an individual telegraph receiver.

14. In combination with a telephone system, a

first source of oscillations, means for keying said, oscillations i8 accordance with a telegraph code to produce trains of oscillations, a second source of oscillations, means for: modulating said second oscillations by said keyed oscillations, means responsive to said modulated oscillations to pro:

duce tone, signals. and a telephone transmitter connected to the telephone system and disposed in sound receiving relation to said tone producing means. i j I 15'. In combinationwith av telephone system, a first source of oscillations, means for keying said "oscillations in'accordance with a telegraph code to produce trains'of oscillations, a second source of oscillations, means for modulating said second oscillaticnsby said keyedoscillations, means responsive to said modulatedoscillations to produce tone signals, a telephone transmitter for said I telephone system disposed'in sound receiving relation to said tone producing means, a sound mesponsive device disposed in sound receiving relation to the distant receiver of said telephone system for producing oscillations in accordance with received tone'signals, and means for do? modulating said latter-oscillations to produce telegraphic code impulses.

16. In combination with a telephone system, a

first source 'of oscillations, means for keying said oscillations in accordance with a telegraph code, a second source of oscillations of a frequency near the upper range of efiicient telephone transmission, means for modulating, said second oscillations by said keyed oscillations, a first filter for suppressing oscillations of frequencies substantially below the frequency of said second source of oscillations, a voice responsive device for producing voice frequency currents, a second filter associated therewith for suppressing voice frequency currents in the range efiiciently passed by said first filter, a sound producing device. means for impressing said filtered telegraphically modulated oscillations and said filtered voice frequency currents on. said sound producing device,

- telephone system, disposed in sound receiving and a telephone transmitter forming part of said relation to said sound producing device. a

17. In combination with a telephone system. a first source of oscillations, means for keying said oscillations in accordance with a telegraph code, a second source of oscillations of a frequency near the upper range of efiicient telephone transmission, means for modulating said second oscillations by said keyed oscillations, a first filter for suppressing oscillationsof frequencies substantially below the frequency of said second source of oscillations, a voice responsive device for producing voice frequency currents, a second filter- ,associaied therewith for suppressing voice fre;--

quency currents in the range efiic'iently passed by" said first filter, sound producing means responsive to said filtered telegr'aphically moduated oscillations and said filtered voice frequency currents, a telephone forming-part of said telephone system, disposed in mud receiving relation to said sotmdproduc'ing means, a sound responsive device 'dismd in sound rerelation to the distant receiver of said telephone systemforpi' lw l oecillationsin ."saidreceivedoscillationsonsaidthirdandfoiurth '70 accordance with received $0116 M, I third filter for suppressing oscillations of a frequency substantially below the frequency of said second source of oscillations, a fourth filter for suppressing frequencies in the range; eificiently passed by said third filter, means for imprusing filters,meansintheou tputofsaidthirdfilter for demodulating the thereby to means for producing tone signals in accordance I with a telegraphcode, means for impressing said tone signals on the transmitter of said telephone system concurrently with voice signals and means associated with the distant receiver of said telephone system for separating said tone signals and said voicesignals whereby simultaneous telegraph v and telephone communication may be conducted over the telephone system.

19. In combination with a telephone system .adapted for ordinary telephone conversation,

means for impressing voice currents thereon, meansfor concurrently transmitting audible telegraph signals thereover, with said telephone signals, and means restricting the frequency components of the voice currents to aportion of the audible band below the frequency of the telegraph signalling currentfor preventing interference of said telephone and telegraph signals with each other. I I

20. In combination with a telephone system, plural-channel means for concurrently transmitting a plurality of audible telegraph signals over' said system, means for preventing interference between said signals in separate channels and.

22. The method of communication over a telephone system which comprises generating electrical oscillations of two different frequencies,

. producing therewith permutation code telegraph signals having frequency components in the range emciently transmitted by the telephone system. said last-mentioned step including the step of modulating the oscillations of one frequency by the other, transmitting said. signals over the telephone system and filtering, rectifying and detecting said signals.

23. The method of communication over a telephone channel which comprises producing telegraphically modulated oscillations of frequency near the upper range of efiicient telephone transmission and voice currents having frequencies approximating that .of said oscillations suppressed, concurrently impressing said oscillations and voice currents on the telephone channel and filtering the received oscillations from the received voice currents. v

24. In a combined telephone-telegraph system, a circuit, means for concurrently transmitting audible-tone telegraph signals and voice currents over said circuit, the frequency components of said telegraph signals and voice currents being limited to less-than 3000 cycles per second and means for preventing interference of said telegraph signals and voice currents with each other. 26. In a combined telegraph-telephone system,

a telephone circuit, means for producing electrical of. a predeterminod1requency.;means for keying said oscillations in accordance with a telegraph code, means for producing electrical of a, higher frequency, not exceeding- 9000 cycles per second, meansfor modulating said 75 higher frequency oscillations in accordance with said keyed oscillations, means for filtering said modulated oscillations to eliminate the first mentioned lower irequency oscillations, and means electrically independent of the telephone equipment for impressing signalling currents corresponding to said filtered oscillations upon saidtelephone circuit. A

26. In a combined telephone-telegraph system, a telephone transmitter, means for producing. telegraphically modulated oscillations of a frequency band near the upper range of efllcient telephone transmission, means for producing voice frequency signals having the frequencies 1 within said band suppressed and means,'including said telephone transmitter, for impressing said telegraphically modulated oscillations and i said voice frequency signals on the telephone system.

27. In a combined telephone-telegraph system, a telephone circuit, means for producing telegraphically modulated oscillations of a frequency band near the upper range of efficient telephone transmission means for producing voice frequency signals having the frequencies within said band suppressed, and means electrically independent o! the telephone systemfor impressing said telegraphicaily modulated oscillations and said voicelirequency signals on said telephone circuit.

' 28. In a combined telephone-telegraph system,

a telephone sub-station, means at said sub-station tor producing telegraphicallv modulated oscillationa of a frequency band near the upper range of ei'llcient telephone tron, means at said sub-station for producing voice currents having the frequencies within said band sup: pressed, means for impressing said telegraphically modulated oscillations and voice currents on the telephone system, ,means at a remote point in the system for separating the received voice currents and telegraphic'ally modulated signals, a sound reproducer responsive to said voice currents, a recorder, and means for operating said recorder in accordance with the receivedtelegraphically modulated signals.

29. In combination with a telephone system, a telephone sub-station, a first source of oscillations, means for keying said oscillations in accordance with a telegraph code tov produce trains or oscillations, a second source of oscillations at said sub-station, means for modulating said second source by said keyed oscillations, means responsive to said modulated oscillations to produce tone signals, a telephone transmitter at said sub-station connected to the telephonevsystem and arranged in sound receiving relation to said tone signal producing means and means at a remote point in the telephone system for eilecting a record of said signals. a

. FERNAND E. nI-IUMY.

rlawauiscrv w. mm.

, 25 30. In a combined telephone-telegraph system, a telephone circuit, means for impressing voice 

